U.S. patent number 3,758,949 [Application Number 05/104,381] was granted by the patent office on 1973-09-18 for digitizer.
Invention is credited to Charles A. Fausel, Allan A. Lorenz.
United States Patent |
3,758,949 |
Fausel , et al. |
September 18, 1973 |
**Please see images for:
( Certificate of Correction ) ** |
DIGITIZER
Abstract
Digital readout data of coordinates of points in a two
dimensional system is generated in a pair of counters in response
to the angular positions of the following: (1) a first disc
rotatable in response to movement of a first slider in a straight
path to a selected position, and (2) a second disc rotatable in
response to movement of the first slider and in response to
movement of a second slider in a straight path to a selected
position. The second slider is carried from the first slider and
arranged for movement therewith and normally thereto independently
thereof. Effect on readout due to movement of the second slider
resulting from the movement of the first slider is prevented
because the discs are mounted for rotation simultaneously upon
movement of the first slider. A sensing assembly adapted for
detecting the relative angular displacement of the second disc and
actuating an associated counter is carried with said first disc for
rotation relative to the second disc.
Inventors: |
Fausel; Charles A. (Chicago,
IL), Lorenz; Allan A. (Willowick, OH) |
Family
ID: |
22300206 |
Appl.
No.: |
05/104,381 |
Filed: |
January 6, 1971 |
Current U.S.
Class: |
33/1M; 250/233;
250/231.14 |
Current CPC
Class: |
G06F
3/0312 (20130101) |
Current International
Class: |
G06F
3/033 (20060101); G09b 029/10 () |
Field of
Search: |
;33/1M ;235/61.6A |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Hull; Robert B.
Claims
We claim:
1. In a digitizer wherein transducing means, supported on a
stationary base, comprises a first member having at least one
annular face portion and mounted for rotation relative to said base
about the axis of said face portion in response to movement of a
first element along a first straight course relative to said base,
and a second member having at least one annular face portion and
mounted for rotation relative to said base about said axis of said
last-mentioned face portion in response to said movement of said
first element and to relative movement between said first element
and a second element carried with said first element, said second
element being movable relative to said first element along a second
course extending along said first element perpendicularly to said
first course, and wherein the transducing means further includes
means for displaying for each of said members a separate symbol,
said symbols respectively being representative of the angular
displacements of, the first member relative to an initial angular
reference position thereof fixed relative to the base, and of the
second member relative to an initial angular reference position
thereof fixed relative to the first member, in response to and
correlated with any movement of the associated one of said first
and second elements, relative to an initial reference position
thereof, along the associated one of said first and second straight
courses, the improvement comprising:
means for rotating: (1) said second member independently of said
first member in response to linear movement of said second element
along said second course, and (2) said first and second members
simultaneously in response to linear movement of said first
element, and
means for preventing an effect on said displaying means resulting
from movement of said second member in consequence of movement of
said first element, said last-mentioned means including:
first means, fixed to said base, for sensing the angular
displacement of said first member, relative to said initial angular
reference position thereof, and
second means, comprising a photosensor arranged for rotation with
said first member, for sensing the angular displacement of said
second member only when it is relative to said first member.
2. A combination according to claim 1 wherein said means for
rotating comprises a rotatable shaft and a cylinder mounted for
rotation concentrically with said shaft, said first member being
rotatable relative to said base in response to movement of said
first element relative to said base and being secured to said
shaft, said second member being rotatable in response to movement
of said first element relative to said base and to movment of said
second element relative to said first element and being carried by
said cylinder.
3. Apparatus for providing digital display of coordinate points of
a two dimensional plane and comprising:
a stationary base;
a first slider mounted on said base and arranged for movement in a
first linear path relative thereto;
a second slider mounted on said first slider for movement relative
thereto in a second linear path extending perpendicularly to said
first path;
a first supporting element mounted for rotational movement relative
to said base and drive-coupled to said first slider;
a first member mounted on said first supporting element for
rotation therewtih;
first pulley-cable drive coupling means for rotating said first
member relative to aid base through an angle in response to and
corresponding to the linear distance of movement of said first
slider;
a second supporting element mounted for rotational movement
relative to said base and drive-coupled to said second slider;
a second member mounted coaxially of said first member on said
second supporting element for rotation therewith;
second pulley-cable drive coupling means for rotating said second
member relative to said base through an angle in response to and
corresponding to the linear distance of movement of said second
slider plus the linear distance of movement of said first slider,
and
means for sensing the angular distance through which said first
member moves, relative to said base, with said second member, in
response to movement of said first slider relative to said base,
and for sensing the angular distance through which said second
member moves, relative to said first member, in response to
movement of said second slider relative to said first slider, said
means for sensing comprising first and second sensing assemblies,
said first sensing assembly being fixed on said base adjacent said
rotatable first member, and said second sensing assembly being
mounted for rotation with said first member independently of
rotation of said second member.
4. Apparatus according to claim 3 wherein each of said members is a
disc having a plurality of arcuately spaced apart apertures, said
first sensing assembly comprising a first lamp and a first
photosensor aligned for exposure to said first lamp through
apertures in said first disc for counting the angular distance of
its rotation, and said second sensing assembly being secured to
said first supporting element and comprising a second lamp and a
second photosensor aligned for exposure to said second lamp through
apertures in said second disc for sensing the angular distance of
its rotation relative to said first disc.
5. A combination according to claim 3 wherein said second member is
arranged for movement in response to movement of said first slider
and wherein said means for sensing includes a first sensor assembly
fixed on said base adjacent said first rotatable member for
registering the rotation of said first member relative to said
base, and a second sensor assembly arranged for rotation with said
first member and responsive to the rotation of said second member
relative to said first member.
6. A digitizer comprising:
a stationary base;
first and second elements mounted on said base for movement
relative to said base along orthogonal paths, said second element
carried by said first element;
a separate cable connected to each of said elements;
a first member connected to said first element through one of said
cables for rotation about an axis of rotation relative to said base
in response to movement in one of said paths;
a second member connected to the other cable and mounted parallel
to said first member for coaxial rotation about said axis relative
to said first member in response to movement of said second element
linearly in the other of said paths and independently of any
movement of said first element in said one path;
means for generating a first output in response to the angular
distance through which said first member rotates relative to said
base, and
means for generating a second output in response to the angular
distance through which said second member rotates relative to said
first member, said last-mentioned means being mounted for rotation
with said first member about said axis so as to prevent the
generation of said second output in response to the angular
distance through which said second member rotates by reason of
movement in only said one of said paths.
7. A combination according to claim 6 wherein said second output
generating means comprises a pulse generator, and said preventing
means comprises means rigidly securing said pulse generator to said
first member for rotation about said axis, said pulse generator
being responsive to rotation of said second member relative to said
first member for generating said second output.
8. A combination according to claim 7 wherein said pulse generator
comprises a photosensor and a lamp supported in operable alignment
with said second member and wherein said second member is a disc
having arcuately spaced apart openings through which said
photosensor is successively and interruptedly exposed to said lamp
only upon movement of said second element independently of movement
of said first element.
9. A combination according to claim 8 wherein said first output
generating means comprises another pulse generator comprising
another lamp and photosensor photo-sensor fixedly supported on said
base in operable alignment with said first member, and wherein said
first member is another disc having arcuately spaced openings
through which said other photosensor is successively and
interruptedly exposed to said other lamp during all continuous
movement in said first path.
10. A combination according to claim 9 further characterized by
means for counting generated pulses according to the direction of
rotation of said members, each relative to its associated
photosensor.
11. A combination according to claim 10 wherein said counting means
comprises a pair of up-down switches including sensors arranged for
response to the direction of rotation of each disc relative to its
associated photosensor.
12. A combination according to claim 6 wherein said first output
generating means comprises a pulse generator mounted on said base
adjacent said first member.
Description
BACKGROUND OF THE INVENTION
This invention relates to a digitizer apparatus adapted for
obtaining a digital readout of orthogonal coordinates of points in
a two dimensional or planar system. It is adaptable as a drafting
instrument in which function it has been conventionally and
variously referred to as an apparatus for layout, plotting or
drafting.
A known digitizer has a pair of rotatable members, each of which is
associated with one of a pair of orthogonal coordinates and is
arranged for rotation about its axis in response to a slider
movement in a straight path longitudinally of one of said
coordinates. The agency or transducer for translation of the linear
movement of each slider to angular movement of an associated
rotatable member comprises a pulley. Readout of the coordinates of
the points is generated according to the angular conditions of the
rotatable members.
However, the sizes of the rotatable members are restricted because
they are required to be mounted at or near the plotting plane of
the digitizer, with one thereof on a slider. This limitation
relates to digitizer accuracy which is a function of the size of
the rotatable members, accuracy increasing in proportion to
increase in size. Other approaches to high accuracy lead to very
high cost.
It is an object of the present invention to provide a new and
improved digitizer.
It is another object of the invention to remove restraints on
digitizer accuracy as a function of cost by reason of transducer
location.
It is a further object of the invention to maximize digitizer
accuracy without corresponding increase in work area
requirement.
SUMMARY OF THE INVENTION
To achieve the foregoing, and other objects of the invention which
will become apparent from the ensuing description, transducing
means in a digitizer comprises a first member mounted for rotation
in response to movement of a first element along a first straight
course and a second member which is mounted for rotation in
response to a second element carried with said first element for
movement along a second course defined by said first element
normally to said first course. A display shows a symbol
representative of the angular condition of each member. Means are
provided for rotating said second member simultaneously with said
first member in response to movement along said first course to
prevent an effect on the display due to movement of said second
element resulting from movement of said first element.
Considered from another aspect, the aforesaid objects are effected
through the agency of a digitizer which has an axis of rotation. A
first member is mounted for rotation about said axis in response to
linear movement in a first straight path. A second member is
mounted coaxially and parallel to said first member for rotation
about said axis in response to linear movement in said first
straight path and in a second straight path normal to said first
straight path. Means are provided for generating a first output in
response to the angular distance through which said first member
rotates. Means are provided for generating a second output in
response to the angular distance through which the second member
rotates by reason of movement in said second straight path. Means
are provided for preventing output in response to the angular
distance through which the second member rotates by reason of
movement in said first straight path.
BRIEF DESCRIPTION OF THE DRAWINGS
In the ensuing detailed description of the invention, reference is
had to the accompanying drawing, in which:
FIG. 1 is a top plan view of a digitizer embodying the present
invention;
FIG. 2 is a side elevational view of said digitizer according to
line 2--2 of FIG. 1 and showing a first slider, parts being broken
away for the purpose of illustration;
FIG. 3 is a detailed view in vertical section according to line
3--3 of FIG. 2;
FIG. 4 is a detailed view in vertical section according to line
4--4 in FIG. 3;
FIG. 5 is an enlarged view of transducer means comprising said
digitizer according to the line 5--5 of FIG. 2;
FIG. 6 is a vertical sectional view of the transducer means
according to line 6--6 of FIG. 5;
FIG. 7 is a view of a second slider comprising said digitizer
according to line 7--7 of FIG. 1; and
FIG. 8 is a vertical sectional view according to the line 8--8 of
FIG. 5 and illustrating a switch for up and down counting.
DETAILED DESCRIPTION OF THE INVENTION
Referring now more particularly to FIG. 1, shown is a digitizer
generally designated 10. It comprises a first element or slider 12
having opposed end portions 14 and 16 and a body or medial section
18 which extends transversely of a rectangular table or drafting
board 20, adjacent parallel sides 22 and 24 of which end portions
14 and 16 are disposed.
A pair of parallel rails 26 and 28 extending parallel to and
adjacent sides 22 and 24 of table 20 support slide 12 adjacent
through superposed from and parallel to the table for movement in a
first straight path or course longitudinally of and defined by said
rails (in the Y direction according to the arrows in FIGS. 1 and
2). For that purpose, end portion 16 is a cylinder, being
journalled about the rail 28; and end portion 14 is fashioned as a
trolley, having a pair of grooved wheels 30 and 32 (FIG. 4) which
frictionally engage against the upper surface of rail 26, and
having a lower grooved wheel 34 which frictionally engages against
the lower surface of said rail. Wheels 30 and 32 are rotational
about a pair of pins 36 and 38 which are spaced apart
longitudinally of said rail; and wheel 34 is rotational about a pin
40 disposed medially of the pins 36 and 38 whereby movement of the
slide longitudinally of said first straight course will be
smooth.
A second element or slider 44 (FIGS. 1 and 7) is carried from
slider 12 for movement therewith in the Y direction as said first
slider moves longitudinally of the first path The second slider is
also adapted to move longitudinally of body 18, independently of
slider 12, in a second straight path or course defined by said body
and disposed perpendicular to the first course (arrow X in FIG. 1).
In the illustrated embodiment, the second slider has a pair of
depending pins 46 and 48 (FIG. 7) which are spaced apart in a
direction of elongation of rails 26 and 28. A pair of grooved
rollers 50 and 52 are rotationally mounted on said pins, their
grooves being proportioned for rotationally engaging opposed
parallel sides 54 and 56 of body 18 whereby said second slider is
supported superposed and parallel to table 20 for movement
longitudinally of said body.
For tracing a pattern 58 (FIG. 1) on, for example, a sheet 60
secured in a plane, adjacent and parallel to table 20, a scribe or
suitable pointed locating element 62 is rigidly secured by any
suitable means to and depends from slider 44. To provide a readout
of the coordinates of points in a trace made by the scribe, in
accordance with the present invention, transducer means herein
comprises a first transducer generally designated 64 (FIG. 5)
responsive to movement in the Y direction and a second transducer
generally designated 66 and responsive to movement in the X
direction. The transducers are characterized by corresponding
rotatable assemblies herein shown including discs 68 and 70 which
are arranged for rotation about a common axis 71 defined by a first
rotatable support element or shaft 72. However, disc 70 is
rotatable independently of disc 68, being secured to a second
rotatable support element, cylinder or hollow shaft 74 which is
circumposed for rotation about shaft 72.
In the exemplary embodiment, transducers 64 and 66 are mounted
within a housing 76 (FIG. 1 and 2) which is supported adjacent
table 20 on an extension 78 thereof. Within the housing the opposed
end portions of shaft 72 rotationally are supported in a pair of
spaced apart journalling blocks 80 and 82 which project vertically,
upwardly from a base or floor 84 (FIGS. 2 and 5) of the
housing.
A hub 85 of disc 68 is rigidly secured to shaft 72 by a suitable
fastener such as a set screw 86, whereby disc 68 is constrained for
rotation with said last shaft. A sheave 88 comprising pulley means,
herein shown fastened integrally with said hub, translates the
linear movement of slider 12 in the y direction into angular
movement of disc 68 about axis 71. This is achieved through the
agency of a belt or cord 90 (FIGS. 2 and 5) included in said pulley
means and which is disposed in a plane and has a lower course with
a medial portion 91 frictionally coiled about sheave 88. Opposed
end portions 92 and 94 of said cord (FIGS. 1 and 2) are secured to
opposite end portions of slider end portion 14 and in alignment
parallel to rails 26 and 28 by suitable fasteners 96 and 98. Said
cord is also entrained about a pair of guide wheels 100 and 102.
They are mounted in spaced apart relationship longitudinally of the
first path parallel to side 22 of the table 20 such that upper and
lower belt courses 101 and 103 are disposed in a plane parallel to
rails 26 and 28 and parallel to sheave 88. Accordingly, as the
slider 12 moves to the right (as seen in FIG. 2), disc 68 will
rotate clockwise. The arrangement is such that, for each linear
position of said last slider, there is a corresponding angular
position of disc 68 about said axis.
Means for generating a first output in response to the angle
through which disc 68 rotates comprises a counting or sensing
assembly 105 (FIG. 5) which includes a first photosensor 104 and a
lamp 106. They are secured to housing base 84, being disposed on
opposite sides of said disc and proportioned such that they are
operably aligned through any of a plurality of apertures 108 in the
peripheral end portion of said disc. In consequence of the
foregoing arrangement, as disc 68 is rotated in any selected
direction, the light from the associated lamp will impinge on the
photosensor through apertures 108 as a succession of light
impulses, interrupted by the fabric of the disc, and will cause the
photosensor, as means for counting disc apertures, to generate a
succession of responsive outputs through one of its leads 110.
These outputs actuate registering means, herein shown as an
"up-down" counter 112 (FIG. 1), which may be a binary or a ring
counter of conventional construction, whereby predetermined
increments of movement of slide 12 in the Y direction will have
distinctive numerical representations or symbols visible at a
display 114 of said counter.
Counting up or down according to the direction of rotation depends
on the state of an up-down switch 115 (FIGS. 5 and 8). Herein said
switch is carried from one end portion of an arm 116, the opposite
end portion of which is secured to block 82 by a fastener 118. The
switch has an "up" counting state when shaft 72 rotates clockwise
(with respect to FIG. 8) and a "down" counting state when the shaft
rotates counterclockwise. The direction of rotation is detected by
a switch sensor 120 which rides along the surface of a collar 121,
said collar being secured to the shaft 72. The arrangement is such
that, as the shaft rotates clockwise the sensor is urged upwardly
and when the shaft rotates counterclockwise the sensor is urged
downwardly. One state of the switch corresponds to each position of
the sensor; and a corresponding "count up" or "count down" signal
from said switch through a lead 122 to counter 112 produces a
corresponding up or down counter counting mode.
Another up-down switch 126 is supported from arm 116, for detecting
the direction of movement of the second slider 44 in the X
direction. The switch 126 is responsive to the direction of
rotation of disc 70. Its sensor arm 128 rides against a collar 130
and is movable upwardly and downwardly according to the direction
of rotation of the outer, hollow shaft 74 on which said last collar
is rigidly secured. Like switch 114, switch 126 is adapted to
provide a selected one of a pair of signals depending upon the
position of its sensor. By conventional means (not shown), said
last switch is adapted to impose its outputs on registering means
comprised of a second "up-down" counter 132 (FIG. 1), similar to
the counter 112, to set its mode such that its display 134 will
count up or down depending upon the direction of rotation of disc
70, corresponding to increments of movement of the second slider 44
in the X direction.
In the exemplary embodiment, the hollow shaft 74 is part of an
integral assembly retained from shifting longitudinally of said
shaft by a pair of retainers 136 and 138 (FIG. 5). Disc 70 is
included at one end of said assembly, said disc being disposed
parallel to disc 68. A sheave 139 comprising pulley means is
fashioned at one end of the hub 140 of disc 70. Frictional
engagement of a belt or cord 142 included in said pulley means and
entrained about said sheave results in rotation of disc 70. By
reason of the connection of said cord and slider 44, a description
of which will be amplified on hereinafter, disc 70 has an angular
condition and counter 132 displays a distinctive numerical
representation corresponding to each predetermined increment of
position of slider 44 along the body 18 of the first slider 12.
To effect the translation of the linear motion of the slider 44
into rotation of disc 70, the opposite end portions 144 and 146
(FIG. 1) of the cord 142 are rigidly secured by suitable fasteners
148 and 150 to the slider 44 in spaced apart positions aligned
longitudinally of body 18. From fastener 150, a stretch 152 of the
cord extends toward rail 28 in alignment with both fasteners and
along body 18. A guide roller 154 carried on said body adjacent end
portion 16 and about which said cord is entrained separates stretch
152 from a parallel stretch 156 of the cord which extends through
or under the slider 44 (FIG. 7) along body 18 to end portion 14 of
slider 12. Thereat cord 142 changes course about a guide roller 158
carried on said last end portion and into a stretch 160 extending
outwardly from said end portion parallel to rail 26. From fastener
148 a stretch 162 of the cord extends along body 18 parallel to
stretch 156 and in alignment with stretch 152 toward rail 26. A
guide roller 163 carried from said last end portion and spaced from
roller 158 longitudinally of rail 26, changes the course of the
cord from stretch 162 into a stretch 164. The latter is aligned
with and extends from slider 12 outwardly in a direction opposite
to stretch 160. Stretch 160 and 166 define the upper course of a
loop 165 which is disposed in a plane parallel to the rails 26 and
28 and has a lower course with a medial portion 161 (FIG. 5)
frictionally coiled about sheave 139 for rotating disc 70
responsively to movement of slider 44.
Means for generating a second output, this in response to the
angular distance through which disc 70 rotates by reason of
movement in the second path, comprises a counting or sensing
assembly 167, which includes a second photosensor 169 (FIG. 5) and
a lamp 168. They are disposed on opposite sides of disc 70 and are
aligned through any of the regularly and arcuately spaced apart
apertures 170 in the peripheral end portion of said disc (FIG. 6).
In consequence of the foregoing arrangement, as disc 70 is rotated
in any selected direction relative to assembly 167, the light will
impinge on said photosensor through apertures 170 as a succession
of light impulses, interrupted by the fabric of said disc, and will
cause the photosensor, as means for counting disc apertures, to
generate a succession of responsive outputs to counter 132 for
counting increments of movement of the second slider 44 in the X
direction.
Consider now operation of the digitizer. Assume slider 12 is moved
longitudinally along the first course, for example, upwardly with
respect to FIG. 1, from any one position to any other position. In
consequence thereof, sheave 139 will rotate to rotate the
transducer disc 70. However, slider 44 will retain its same
relative position with respect to body 18. While the movement of
slider 12 lengthens stretch 160 of belt 142, the increase in length
is at the expense of stretch 164 which becomes shortened
correspondingly, the relative position of the sliders 12 and 44
remaining unaffected.
Means for preventing output in response to the angular distance
through which disc 70 rotates by reason of movement of slider 12 in
its first path along rails 26 and 28 comprises a securance of the
sensing assembly 167 to shaft 72. To achieve the securance, a
vertically extending arm 172 (FIGS. 5 and 6) parallel to disc 70
supports sensor 169 and an offset extension 174 of said arm
supports lamp 168. An electrically insulative sleeve 176, about
which the lower end portion of said arm is rigidly secured, is
itself coaxially secured to the outer surface of shaft 72 for
rotation therewith.
The diameters of disc 68 and 70 are equal. The disposition and size
of apertures 108 and 170 in either of the discs is the same as in
the other thereof. In consequence, when slider 12 moves either to
or fro, though disc 70 rotates, there will be no relative
displacement between assembly 167 and said last disc and therefore
no change in the X-counter 132. That counter will only count when
slider 44 moves independently of slider 12.
Lamp 168 is in an electrical circuit with input and output leads
180 and 182 which have portions extending axially through sleeve
176. Photosensor 169 is in an electrical circuit with input and
output leads 184 and 186 which have portions extending axially
through sleeve 176. A plurality of conductive axially spaced
terminal rings 188, 190, 192, and 194 are circumposed about sleeve
176 to which they are secured rigidly and with which they are
rotatable. Each ring is electrically connected to one of the leads
180, 182, 184, and 186 in the manner shown for the connection
between lead 186 and ring 194 (FIG. 6). A fixed bracket 196
projects upwardly from floor 84 and supports a terminal holder 198.
A bank of flexible terminals or sensors 200, 202, 204 and 206 are
fashioned as leaf springs and project from holder 198 such that
each thereof maintains continuous electrical contact with one of
the rings 188, 190, 192, and 194, regardless of the angular
condition of shaft 72. Each of said sensors is electrically
connected in holder 198 to a wire 207 only one of which is shown in
FIG. 6. Through wires 207 associated with rings 188 and 190, lamp
168 is connected to opposed sides of a power source (not shown).
Through wires 207 associated with rings 192 and 194 photosensor 169
is connected to the input side of counter 132.
It is observed that transducers 64 and 66 are spaced from the table
20. Moreover, they are spaced from sliders 12 and 44; and while
they are shown at or near table level, such arrangement is not
critical to the invention and other suitable positions may be
selected. For example, the transducers may be suitably suspended
from beneath table 20. Thereby, the discs 68 and 70 and sheaves 88
and 139 could be enlarged appreciably to provide greater levels of
digitizer accuracy without increased sensor sophistication and
without increase in work area requirement.
As many modifications in the described construction could be
conceived, and as many changes could be made therein without
departing from the spirit and scope of the invention, it is
intended that all matter contained in the accompanying
specification shall be considered as illustrative only and not in a
limiting sense.
* * * * *